/*
 * Register cache access API - rbtree caching support
 *
 * Copyright 2011 Wolfson Microelectronics plc
 *
 * Author: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/slab.h>
#include <linux/device.h>
#include <linux/debugfs.h>
#include <linux/rbtree.h>
#include <linux/seq_file.h>

#include "internal.h"

static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
                                 unsigned int value);
static int regcache_rbtree_exit(struct regmap *map);

struct regcache_rbtree_node {
        /* the actual rbtree node holding this block */
        struct rb_node node;
        /* base register handled by this block */
        unsigned int base_reg;
        /* block of adjacent registers */
        void *block;
        /* number of registers available in the block */
        unsigned int blklen;
} __attribute__ ((packed));

struct regcache_rbtree_ctx {
        struct rb_root root;
        struct regcache_rbtree_node *cached_rbnode;
};

static inline void regcache_rbtree_get_base_top_reg(
        struct regmap *map,
        struct regcache_rbtree_node *rbnode,
        unsigned int *base, unsigned int *top)
{
        *base = rbnode->base_reg;
        *top = rbnode->base_reg + ((rbnode->blklen - 1) * map->reg_stride);
}

static unsigned int regcache_rbtree_get_register(
        struct regcache_rbtree_node *rbnode, unsigned int idx,
        unsigned int word_size)
{
        return regcache_get_val(rbnode->block, idx, word_size);
}

static void regcache_rbtree_set_register(struct regcache_rbtree_node *rbnode,
                                         unsigned int idx, unsigned int val,
                                         unsigned int word_size)
{
        regcache_set_val(rbnode->block, idx, val, word_size);
}

static struct regcache_rbtree_node *regcache_rbtree_lookup(struct regmap *map,
        unsigned int reg)
{
        struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
        struct rb_node *node;
        struct regcache_rbtree_node *rbnode;
        unsigned int base_reg, top_reg;

        rbnode = rbtree_ctx->cached_rbnode;
        if (rbnode) {
                regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
                                                 &top_reg);
                if (reg >= base_reg && reg <= top_reg)
                        return rbnode;
        }

        node = rbtree_ctx->root.rb_node;
        while (node) {
                rbnode = container_of(node, struct regcache_rbtree_node, node);
                regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
                                                 &top_reg);
                if (reg >= base_reg && reg <= top_reg) {
                        rbtree_ctx->cached_rbnode = rbnode;
                        return rbnode;
                } else if (reg > top_reg) {
                        node = node->rb_right;
                } else if (reg < base_reg) {
                        node = node->rb_left;
                }
        }

        return NULL;
}

static int regcache_rbtree_insert(struct regmap *map, struct rb_root *root,
                                  struct regcache_rbtree_node *rbnode)
{
        struct rb_node **new, *parent;
        struct regcache_rbtree_node *rbnode_tmp;
        unsigned int base_reg_tmp, top_reg_tmp;
        unsigned int base_reg;

        parent = NULL;
        new = &root->rb_node;
        while (*new) {
                rbnode_tmp = container_of(*new, struct regcache_rbtree_node,
                                          node);
                /* base and top registers of the current rbnode */
                regcache_rbtree_get_base_top_reg(map, rbnode_tmp, &base_reg_tmp,
                                                 &top_reg_tmp);
                /* base register of the rbnode to be added */
                base_reg = rbnode->base_reg;
                parent = *new;
                /* if this register has already been inserted, just return */
                if (base_reg >= base_reg_tmp &&
                    base_reg <= top_reg_tmp)
                        return 0;
                else if (base_reg > top_reg_tmp)
                        new = &((*new)->rb_right);
                else if (base_reg < base_reg_tmp)
                        new = &((*new)->rb_left);
        }

        /* insert the node into the rbtree */
        rb_link_node(&rbnode->node, parent, new);
        rb_insert_color(&rbnode->node, root);

        return 1;
}

#ifdef CONFIG_DEBUG_FS
static int rbtree_show(struct seq_file *s, void *ignored)
{
        struct regmap *map = s->private;
        struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
        struct regcache_rbtree_node *n;
        struct rb_node *node;
        unsigned int base, top;
        int nodes = 0;
        int registers = 0;
        int this_registers, average;

        map->lock(map);

        for (node = rb_first(&rbtree_ctx->root); node != NULL;
             node = rb_next(node)) {
                n = container_of(node, struct regcache_rbtree_node, node);

                regcache_rbtree_get_base_top_reg(map, n, &base, &top);
                this_registers = ((top - base) / map->reg_stride) + 1;
                seq_printf(s, "%x-%x (%d)\n", base, top, this_registers);

                nodes++;
                registers += this_registers;
        }

        if (nodes)
                average = registers / nodes;
        else
                average = 0;

        seq_printf(s, "%d nodes, %d registers, average %d registers\n",
                   nodes, registers, average);

        map->unlock(map);

        return 0;
}

static int rbtree_open(struct inode *inode, struct file *file)
{
        return single_open(file, rbtree_show, inode->i_private);
}

static const struct file_operations rbtree_fops = {
        .open           = rbtree_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

static void rbtree_debugfs_init(struct regmap *map)
{
        debugfs_create_file("rbtree", 0400, map->debugfs, map, &rbtree_fops);
}
#else
static void rbtree_debugfs_init(struct regmap *map)
{
}
#endif

static int regcache_rbtree_init(struct regmap *map)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        int i;
        int ret;

        map->cache = kmalloc(sizeof *rbtree_ctx, GFP_KERNEL);
        if (!map->cache)
                return -ENOMEM;

        rbtree_ctx = map->cache;
        rbtree_ctx->root = RB_ROOT;
        rbtree_ctx->cached_rbnode = NULL;

        for (i = 0; i < map->num_reg_defaults; i++) {
                ret = regcache_rbtree_write(map,
                                            map->reg_defaults[i].reg,
                                            map->reg_defaults[i].def);
                if (ret)
                        goto err;
        }

        rbtree_debugfs_init(map);

        return 0;

err:
        regcache_rbtree_exit(map);
        return ret;
}

static int regcache_rbtree_exit(struct regmap *map)
{
        struct rb_node *next;
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct regcache_rbtree_node *rbtree_node;

        /* if we've already been called then just return */
        rbtree_ctx = map->cache;
        if (!rbtree_ctx)
                return 0;

        /* free up the rbtree */
        next = rb_first(&rbtree_ctx->root);
        while (next) {
                rbtree_node = rb_entry(next, struct regcache_rbtree_node, node);
                next = rb_next(&rbtree_node->node);
                rb_erase(&rbtree_node->node, &rbtree_ctx->root);
                kfree(rbtree_node->block);
                kfree(rbtree_node);
        }

        /* release the resources */
        kfree(map->cache);
        map->cache = NULL;

        return 0;
}

static int regcache_rbtree_read(struct regmap *map,
                                unsigned int reg, unsigned int *value)
{
        struct regcache_rbtree_node *rbnode;
        unsigned int reg_tmp;

        rbnode = regcache_rbtree_lookup(map, reg);
        if (rbnode) {
                reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
                *value = regcache_rbtree_get_register(rbnode, reg_tmp,
                                                      map->cache_word_size);
        } else {
                return -ENOENT;
        }

        return 0;
}


static int regcache_rbtree_insert_to_block(struct regcache_rbtree_node *rbnode,
                                           unsigned int pos, unsigned int reg,
                                           unsigned int value, unsigned int word_size)
{
        u8 *blk;

        blk = krealloc(rbnode->block,
                       (rbnode->blklen + 1) * word_size, GFP_KERNEL);
        if (!blk)
                return -ENOMEM;

        /* insert the register value in the correct place in the rbnode block */
        memmove(blk + (pos + 1) * word_size,
                blk + pos * word_size,
                (rbnode->blklen - pos) * word_size);

        /* update the rbnode block, its size and the base register */
        rbnode->block = blk;
        rbnode->blklen++;
        if (!pos)
                rbnode->base_reg = reg;

        regcache_rbtree_set_register(rbnode, pos, value, word_size);
        return 0;
}

static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
                                 unsigned int value)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct regcache_rbtree_node *rbnode, *rbnode_tmp;
        struct rb_node *node;
        unsigned int val;
        unsigned int reg_tmp;
        unsigned int pos;
        int i;
        int ret;

        rbtree_ctx = map->cache;
        /* if we can't locate it in the cached rbnode we'll have
         * to traverse the rbtree looking for it.
         */
        rbnode = regcache_rbtree_lookup(map, reg);
        if (rbnode) {
                reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
                val = regcache_rbtree_get_register(rbnode, reg_tmp,
                                                   map->cache_word_size);
                if (val == value)
                        return 0;
                regcache_rbtree_set_register(rbnode, reg_tmp, value,
                                             map->cache_word_size);
        } else {
                /* look for an adjacent register to the one we are about to add */
                for (node = rb_first(&rbtree_ctx->root); node;
                     node = rb_next(node)) {
                        rbnode_tmp = rb_entry(node, struct regcache_rbtree_node,
                                              node);
                        for (i = 0; i < rbnode_tmp->blklen; i++) {
                                reg_tmp = rbnode_tmp->base_reg +
                                                (i * map->reg_stride);
                                if (abs(reg_tmp - reg) != map->reg_stride)
                                        continue;
                                /* decide where in the block to place our register */
                                if (reg_tmp + map->reg_stride == reg)
                                        pos = i + 1;
                                else
                                        pos = i;
                                ret = regcache_rbtree_insert_to_block(rbnode_tmp, pos,
                                                                      reg, value,
                                                                      map->cache_word_size);
                                if (ret)
                                        return ret;
                                rbtree_ctx->cached_rbnode = rbnode_tmp;
                                return 0;
                        }
                }
                /* we did not manage to find a place to insert it in an existing
                 * block so create a new rbnode with a single register in its block.
                 * This block will get populated further if any other adjacent
                 * registers get modified in the future.
                 */
                rbnode = kzalloc(sizeof *rbnode, GFP_KERNEL);
                if (!rbnode)
                        return -ENOMEM;
                rbnode->blklen = 1;
                rbnode->base_reg = reg;
                rbnode->block = kmalloc(rbnode->blklen * map->cache_word_size,
                                        GFP_KERNEL);
                if (!rbnode->block) {
                        kfree(rbnode);
                        return -ENOMEM;
                }
                regcache_rbtree_set_register(rbnode, 0, value, map->cache_word_size);
                regcache_rbtree_insert(map, &rbtree_ctx->root, rbnode);
                rbtree_ctx->cached_rbnode = rbnode;
        }

        return 0;
}

static int regcache_rbtree_sync(struct regmap *map, unsigned int min,
                                unsigned int max)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct rb_node *node;
        struct regcache_rbtree_node *rbnode;
        unsigned int regtmp;
        unsigned int val;
        int ret;
        int i, base, end;

        rbtree_ctx = map->cache;
        for (node = rb_first(&rbtree_ctx->root); node; node = rb_next(node)) {
                rbnode = rb_entry(node, struct regcache_rbtree_node, node);

                if (rbnode->base_reg < min)
                        continue;
                if (rbnode->base_reg > max)
                        break;
                if (rbnode->base_reg + rbnode->blklen < min)
                        continue;

                if (min > rbnode->base_reg)
                        base = min - rbnode->base_reg;
                else
                        base = 0;

                if (max < rbnode->base_reg + rbnode->blklen)
                        end = rbnode->base_reg + rbnode->blklen - max;
                else
                        end = rbnode->blklen;

                for (i = base; i < end; i++) {
                        regtmp = rbnode->base_reg + (i * map->reg_stride);
                        val = regcache_rbtree_get_register(rbnode, i,
                                                           map->cache_word_size);

                        /* Is this the hardware default?  If so skip. */
                        ret = regcache_lookup_reg(map, regtmp);
                        if (ret >= 0 && val == map->reg_defaults[ret].def)
                                continue;

                        map->cache_bypass = 1;
                        ret = _regmap_write(map, regtmp, val);
                        map->cache_bypass = 0;
                        if (ret)
                                return ret;
                        dev_dbg(map->dev, "Synced register %#x, value %#x\n",
                                regtmp, val);
                }
        }

        return 0;
}

struct regcache_ops regcache_rbtree_ops = {
        .type = REGCACHE_RBTREE,
        .name = "rbtree",
        .init = regcache_rbtree_init,
        .exit = regcache_rbtree_exit,
        .read = regcache_rbtree_read,
        .write = regcache_rbtree_write,
        .sync = regcache_rbtree_sync
};